Processing facilities are often managed using process control systems. Example processing facilities include manufacturing plants, chemical plants, crude oil refineries, and ore processing plants. Among other operations, process control systems typically manage the use of motors, valves, and other industrial equipment in the processing facilities. Process control systems routinely include one or more wireless networks containing various wireless devices, such as wireless sensors and wireless actuators.
Often times, the wireless networks used in processing facilities are based on one or more of the IEEE 802.11 standards. While these standards are often suitable for use in monitoring systems that simply monitor industrial equipment in processing facilities, these standards are often inappropriate for use in control systems that actually control the industrial equipment. Some of the reasons include non-deterministic behavior in the Medium Access Control (MAC) layer of 802.11-based mesh networks, packet delays caused by the multi-hop nature of the mesh networks, and the lack of Quality of Service (QoS) support in the MAC layer. Among other things, this means that the delay experienced by one data packet sent through an 802.11-based mesh network can be very different from the delay experienced by another data packet traveling the same path in the network. Conventional 802.11-based mesh networks are unable to provide wireless communications where the end-to-end packet delays and packet losses are upper-bounded under varying network and channel conditions.